Development of a New Thermostable Photosynthetic Bactria by Ricombinant DNA

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In order to develop a new thermostable photosynthetic bacterium, we have investigated the origin of the thermostability in the photosynthetic reaction, and cloning of the photosynthetic reaction center gene for point mutation by recombinat DNA technique.Comparison of protein structures between thermostable photosynthetic bacteria (Chloroflevus aurantiacus, Chromatium tepidum), and mesophilic ones (Chromatium vinosm, Rhodobacter sphaeroides) gave a key to understand the origin. Thermostabel reaction center protein were revealed to have extra structures to keep their thrtiary structure rigid.Genomic DNA was extracted from whole cell of a thermophilic purple sulfur bacterium Chromatium tepidum. From genomic DNA digested by a restriction enzyme Sau 3Al, a gene bank (consist of 800 colonies) was produced by in vitro packaging and transfection to a Ecoli cell. A clone which encodes the photosynthetic reaction center protein for the primary reaction of the photosynthesis was selected and under analysis of the DNA base sequence.Purification of the reaction center protein and trial for crystallization was carried out in order to get three dimensinal structures which are needed to pin point the place to make point mutation for improving thermal stability.